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<div id="msg">
<dl class="meta">
<dt>Revision</dt> <dd><a href="http://trac.webkit.org/projects/webkit/changeset/286049">286049</a></dd>
<dt>Author</dt> <dd>commit-queue@webkit.org</dd>
<dt>Date</dt> <dd>2021-11-18 23:30:40 -0800 (Thu, 18 Nov 2021)</dd>
</dl>

<h3>Log Message</h3>
<pre>Nullptr crash in SimplifiedBackwardsTextIterator::range() via previousSentencePosition
https://bugs.webkit.org/show_bug.cgi?id=229282

Patch by Frédéric Wang <fwang@igalia.com> on 2021-11-18
Reviewed by Darin Adler.

Source/WebCore:

Constructors of TextIterator and SimplifiedBackwardsTextIterator update layout, which may
make HTMLObjectElement switch to fallback content and invalidate their renderer. As a
consequence their advance() method may incorrectly treat them as replaced elements. This
patch updates the layout at the beginning of FrameSelection::modify and disable post
resolution callbacks in order to prevent this kind of unaverted tree changes while browsing
the tree for selection update.

Test: editing/text-iterator/backward-textiterator-object-crash.html

* editing/FrameSelection.cpp:
(WebCore::FrameSelection::modify): Update layout and disable post resolution callback, so that
all iterators used during the execution of the function handle <object>s consistently.

LayoutTests:

Add regression test.

* editing/text-iterator/backward-textiterator-object-crash-expected.txt: Added.
* editing/text-iterator/backward-textiterator-object-crash.html: Added.</pre>

<h3>Modified Paths</h3>
<ul>
<li><a href="#trunkLayoutTestsChangeLog">trunk/LayoutTests/ChangeLog</a></li>
<li><a href="#trunkSourceWebCoreChangeLog">trunk/Source/WebCore/ChangeLog</a></li>
<li><a href="#trunkSourceWebCoreeditingFrameSelectioncpp">trunk/Source/WebCore/editing/FrameSelection.cpp</a></li>
</ul>

<h3>Added Paths</h3>
<ul>
<li><a href="#trunkLayoutTestseditingtextiteratorbackwardtextiteratorobjectcrashexpectedtxt">trunk/LayoutTests/editing/text-iterator/backward-textiterator-object-crash-expected.txt</a></li>
<li><a href="#trunkLayoutTestseditingtextiteratorbackwardtextiteratorobjectcrashhtml">trunk/LayoutTests/editing/text-iterator/backward-textiterator-object-crash.html</a></li>
</ul>

</div>
<div id="patch">
<h3>Diff</h3>
<a id="trunkLayoutTestsChangeLog"></a>
<div class="modfile"><h4>Modified: trunk/LayoutTests/ChangeLog (286048 => 286049)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/LayoutTests/ChangeLog      2021-11-19 07:27:51 UTC (rev 286048)
+++ trunk/LayoutTests/ChangeLog 2021-11-19 07:30:40 UTC (rev 286049)
</span><span class="lines">@@ -1,3 +1,15 @@
</span><ins>+2021-11-18  Frédéric Wang  <fwang@igalia.com>
+
+        Nullptr crash in SimplifiedBackwardsTextIterator::range() via previousSentencePosition
+        https://bugs.webkit.org/show_bug.cgi?id=229282
+
+        Reviewed by Darin Adler.
+
+        Add regression test.
+
+        * editing/text-iterator/backward-textiterator-object-crash-expected.txt: Added.
+        * editing/text-iterator/backward-textiterator-object-crash.html: Added.
+
</ins><span class="cx"> 2021-11-18  Ben Nham  <nham@apple.com>
</span><span class="cx"> 
</span><span class="cx">         Add support for onpushsubscriptionchange event handler
</span></span></pre></div>
<a id="trunkLayoutTestseditingtextiteratorbackwardtextiteratorobjectcrashexpectedtxt"></a>
<div class="addfile"><h4>Added: trunk/LayoutTests/editing/text-iterator/backward-textiterator-object-crash-expected.txt (0 => 286049)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/LayoutTests/editing/text-iterator/backward-textiterator-object-crash-expected.txt                          (rev 0)
+++ trunk/LayoutTests/editing/text-iterator/backward-textiterator-object-crash-expected.txt     2021-11-19 07:30:40 UTC (rev 286049)
</span><span class="lines">@@ -0,0 +1 @@
</span><ins>+This test passes if it does not crash.
</ins></span></pre></div>
<a id="trunkLayoutTestseditingtextiteratorbackwardtextiteratorobjectcrashhtml"></a>
<div class="addfile"><h4>Added: trunk/LayoutTests/editing/text-iterator/backward-textiterator-object-crash.html (0 => 286049)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/LayoutTests/editing/text-iterator/backward-textiterator-object-crash.html                          (rev 0)
+++ trunk/LayoutTests/editing/text-iterator/backward-textiterator-object-crash.html     2021-11-19 07:30:40 UTC (rev 286049)
</span><span class="lines">@@ -0,0 +1,13 @@
</span><ins>+<script>
+  onload = () => {
+      if (window.testRunner)
+          testRunner.dumpAsText();
+      document.documentElement.removeChild(document.head);
+      let input = document.createElement('input');
+      document.documentElement.appendChild(input);
+      getSelection().setBaseAndExtent(input, 0, input, 0);
+      document.body.innerHTML = "<object><object><object><object><div></div></object></object></object></object>";
+      getSelection().modify('move', 'backward', 'sentence');
+      document.body.innerHTML = "This test passes if it does not crash.";
+  };
+</script>
</ins></span></pre></div>
<a id="trunkSourceWebCoreChangeLog"></a>
<div class="modfile"><h4>Modified: trunk/Source/WebCore/ChangeLog (286048 => 286049)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/WebCore/ChangeLog   2021-11-19 07:27:51 UTC (rev 286048)
+++ trunk/Source/WebCore/ChangeLog      2021-11-19 07:30:40 UTC (rev 286049)
</span><span class="lines">@@ -1,3 +1,23 @@
</span><ins>+2021-11-18  Frédéric Wang  <fwang@igalia.com>
+
+        Nullptr crash in SimplifiedBackwardsTextIterator::range() via previousSentencePosition
+        https://bugs.webkit.org/show_bug.cgi?id=229282
+
+        Reviewed by Darin Adler.
+
+        Constructors of TextIterator and SimplifiedBackwardsTextIterator update layout, which may
+        make HTMLObjectElement switch to fallback content and invalidate their renderer. As a
+        consequence their advance() method may incorrectly treat them as replaced elements. This
+        patch updates the layout at the beginning of FrameSelection::modify and disable post
+        resolution callbacks in order to prevent this kind of unaverted tree changes while browsing
+        the tree for selection update.
+
+        Test: editing/text-iterator/backward-textiterator-object-crash.html
+
+        * editing/FrameSelection.cpp:
+        (WebCore::FrameSelection::modify): Update layout and disable post resolution callback, so that
+        all iterators used during the execution of the function handle <object>s consistently.
+
</ins><span class="cx"> 2021-11-18  Antoine Quint  <graouts@webkit.org>
</span><span class="cx"> 
</span><span class="cx">         [Model] add support for pausing and resuming animations
</span></span></pre></div>
<a id="trunkSourceWebCoreeditingFrameSelectioncpp"></a>
<div class="modfile"><h4>Modified: trunk/Source/WebCore/editing/FrameSelection.cpp (286048 => 286049)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/WebCore/editing/FrameSelection.cpp  2021-11-19 07:27:51 UTC (rev 286048)
+++ trunk/Source/WebCore/editing/FrameSelection.cpp     2021-11-19 07:30:40 UTC (rev 286049)
</span><span class="lines">@@ -71,6 +71,7 @@
</span><span class="cx"> #include "SimpleRange.h"
</span><span class="cx"> #include "SpatialNavigation.h"
</span><span class="cx"> #include "StyleProperties.h"
</span><ins>+#include "StyleTreeResolver.h"
</ins><span class="cx"> #include "TypingCommand.h"
</span><span class="cx"> #include "VisibleUnits.h"
</span><span class="cx"> #include <stdio.h>
</span><span class="lines">@@ -1344,6 +1345,14 @@
</span><span class="cx"> 
</span><span class="cx">     willBeModified(alter, direction);
</span><span class="cx"> 
</span><ins>+    // Before modifying selection, update layout and disable post resolution callbacks.
+    // That way, unaverted tree changes are avoided while browsing the document.
+    auto selectionDocument = m_selection.document();
+    if (!selectionDocument)
+        return false;
+    selectionDocument->updateLayoutIgnorePendingStylesheets();
+    Style::PostResolutionCallbackDisabler disabler(*selectionDocument);
+
</ins><span class="cx">     bool reachedBoundary = false;
</span><span class="cx">     bool wasRange = m_selection.isRange();
</span><span class="cx">     Position originalStartPosition = m_selection.start();
</span></span></pre>
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